Image pickup apparatus, image pickup method, exposure control method, and program

An image pickup apparatus comprising:nan image pickup unit configured to generate a long-exposure image signal and a short-exposure image signal from incident light and output the long-exposure image signal and the short-exposure image signal as image pickup signals, the long-exposure image signal being generated by a long exposure period and the short-exposure image signal being generated by a short exposure period, the long exposure period being longer than the short exposure period;a signal processing unit configured to generate a combined image signal by combining the long-exposure image signal and the short-exposure image signal based on a predetermined pixel value switching point, the combined image signal having pixel values less than the predetermined pixel value switching point and greater than the predetermined pixel value switching point, and having a dynamic range that is wider than that of at least any one of the long-exposure image signal and the short-exposure image signal;a detection unit configured to obtain a luminance integrated value of the combined image signal and to generate a luminance histogram of the combined image signal; anda control unit configured to perform exposure correction control for the image pickup unit based on the luminance integrated value and the luminance histogram.

An image pickup method, implemented as an image processing apparatus, comprising:ngenerating a long-exposure image signal by exposure for a long period and a short-exposure image signal by exposure for a short period, the long period being longer than the short period, from incident light transmitted from a subject so as to output the long-exposure image signal and the short-exposure image signal as image pickup signals;generating a combined image signal by combining the long-exposure image signal and the short-exposure image signal based on a predetermined pixel value switching point, the combined image signal having pixel values less than the predetermined pixel value switching point and greater than the predetermined pixel value switching point, and having a dynamic range that is wider than that of at least any one of the long-exposure image signal and the short-exposure image signal;obtaining a luminance integrated value of the combined image signal and generating a luminance histogram of the combined image signal; andperforming exposure correction control based on the luminance integrated value and the luminance histogram.

An exposure correction method for an image pickup apparatus for obtaining a long-exposure image signal by exposure for a long period and a short-exposure image signal by exposure for a short period, the long period being longer than the short period, generating a combined image signal with a dynamic range that is wider than that of at least any one of the long-exposure image signal and the short-exposure image signal by combining the long-exposure image signal and the short-exposure image signal based on a predetermined pixel value switching point, and outputting the generated combined image signal, the exposure correction method comprising:nobtaining a luminance integrated value of the combined image signal and generating a luminance histogram of the combined image signal;detecting occurrence of underexposure in the combined image signal from the luminance histogram;setting a target luminance integrated value on the basis of a detection result of the occurrence of the underexposure;detecting occurrence of overexposure in the combined image signal from the luminance histogram;setting a short-exposure period on the basis of a detection result of the occurrence of the overexposure;performing exposure correction control using the target luminance integrated value and the short-exposure period, andcomparing a pixel value of each pixel with the predetermined pixel value switching point in order for the combined image signal to include pixel values less than the predetermined pixel value switching point and greater than the predetermined pixel value switching point.

A non-transitory computer readable storage medium having stored thereon a computer program that includes instructions for causing an image pickup apparatus to execute exposure correction, the image pickup apparatus being configured to obtain a long-exposure image signal by exposure for a long period and a short-exposure image signal by exposure for a short period, generate a combined image signal with a dynamic range that is wider than that of at least any one of the long-exposure image signal and the short-exposure image signal by combining the long-exposure image signal and the short-exposure image signal based on a predetermined pixel value switching point, and output the generated combined image signal, which when executed by the image pickup apparatus causes a processor to perform an exposure correction method comprising:nobtaining a luminance integrated value of the combined image signal and generating a luminance histogram of the combined image signal;detecting occurrence of underexposure in the combined image signal from the luminance histogram;setting a target luminance integrated value on the basis of a detection result of the occurrence of the underexposure;detecting occurrence of overexposure in the combined image signal from the luminance histogram;setting a short-exposure period on the basis of a detection result of the occurrence of the overexposure;performing exposure correction control using the target luminance integrated value and the short-exposure period, andcomparing a pixel value of each pixel with the predetermined pixel value switching point in order for the combined image signal to include pixel values less than the predetermined pixel value switching point and greater than the predetermined pixel value switching point.